Nitrous Oxide (N₂O) in Urine as Biological Index of Exposure in Operating Room Personnel

Evaluation of personal, environmental and biological exposure of paediatric anaesthetists to nitrous oxide and sevoflurane*

“…Median [interquartile range] 1 h postoperative nitrous oxide concentrations (ppm) in oncology, dental theatre, day surgery unit and MRI suite were: blood, 6 [3][4][5][6][7] [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. .............................................................................................................................................................................................................. Unpaired t-test was applied to determine if there were any significant relationships between blood sevoflurane and nitrous oxide concentration and the type of induction technique, airway management, circuit used or presence of scavenging.…”

“…Sonander et al [14] hypothesised that the urine leaving the kidneys equilibrates rapidly with gas in arterial blood, which in turn, equilibrates rapidly with atmospheric gas levels and concluded it to be a simple and effective method of biological monitoring of exposure to nitrous oxide. Imbriani et al [15] showed some relationship between environmental TWA concentration of nitrous oxide and halothane and corresponding urinary concentrations (r ¼ 0.89 for nitrous oxide; r ¼ 0.92 for halothane) indicating that urinary concentrations could possibly be used as appropriate biological indices. A limited relationship has also been shown among environmental, blood and urinary concentrations of nitrous oxide (r ¼ 0.59 for environment and blood; r ¼ 0.64 for environment and urine; r ¼ 0.71 for blood and urine) [16].…”

Gases and organic solvents in urine as biomarkers of occupational exposure: a review

“…Imbriani et al (1988c) determined the concentrations of N 2 O in 190 operating theatres of 41 hospitals in Italy. Nitrous oxide was detected in the urine of 145 exposed subjects (anaesthetists, surgeons, and nurses).…”

Biomonitoring of exposure to nitrous oxide, sevoflurane, isoflurane and halothane by automated GC/MS headspace urinalysis

“…Moreover, no metabolite is known for N 2 O. For these reasons and for its simplicity, the choice method for assessment of individual exposure should be the determination of non-metabolized anaesthetics in urine rather than the measurement of their concentrations in alveolar air or venous blood [6,10,18,20,21].…”

“…The level of pollution in operating theatres depends ®rstly on the eciency of the active scavenging system, and secondly on multiple factors such as the type of anaesthesiology equipment (close/open systems), the anaesthesiological techniques (high/low¯ow rate, use of face masks or laryngeal mask airways, use of uncued tracheal tubes), and the methods for anaesthetic induction [2,10,15].…”